Precautions for selecting 18650 lithium-ion batteries.
The 18650 battery is a cylindrical standardized lithium-ion battery named after its standardized dimensions (diameter 18 millimeters, length 65 millimeters). This type of battery has the characteristics of high energy density, rechargeable, and multiple chemical systems, and is widely used in consumer electronics, power tools, portable devices, electric vehicles, and other fields.
Due to the fact that 18650 batteries are standard batteries and require a large amount of usage, there is a wide variety of manufacturers and models producing 18650 batteries, ranging from a few cents per unit to tens of yuan per unit. Therefore, when selecting, multiple factors need to be considered comprehensively to ensure the safety, performance, and service life of the battery.
Selection precautions
① Brand selection
Choosing 18650 batteries produced by well-known brands is crucial for safety. Such as Panasonic, Samsung LG、 Sony and other well-known brands, after decades of continuous improvement, have strict quality control systems and comprehensive after-sales services. These brands' batteries are more guaranteed in terms of safety, performance, and lifespan.
② Capacity
The capacity of an 18650 battery is an important criterion for selecting a battery and a key indicator for measuring its ability to store electrical energy, measured in milliampere hours (mAh, which means 1mA discharge current can sustain discharge for 1 hour). The common capacity range is 1000mAh to 3500mAh. The higher the capacity, the stronger the battery's endurance. However, there are a large number of batteries with falsely labeled capacity in the market, and consumers need to be cautious when purchasing. Generally speaking, the actual capacity of domestically produced 18650 batteries is between 800mAh and 3500mAh. To ensure the true capacity of the battery, it is recommended to purchase samples and use a discharge tester for testing.
③ Continuous discharge current
Continuous discharge current (CDR) refers to the maximum current that a battery can continuously output without damaging itself, usually expressed as the C number. For example, a 2800mAh 18650 battery with a continuous discharge capacity of 0.5C has a continuous discharge current of 1.4A. If the device requires a higher discharge current, a battery with a higher C number should be selected.
④ Internal resistance
Internal resistance is the size of the battery's own resistance. The smaller the internal resistance, the stronger the battery's discharge ability and the less energy loss it has. Generally speaking, the internal resistance of high-quality 18650 batteries should be less than 100m Ω. Excessive internal resistance not only affects the performance of the battery, but may also cause overheating and even safety issues. Therefore, when purchasing, attention should be paid to the internal resistance parameters of the battery.
⑤ Voltage
The standard voltage for 18650 batteries is usually 3.7V, with a charging cut-off voltage of 4.2V. However, some batteries may have different nominal voltages, such as lithium iron phosphate (LFP) 18650 batteries with a nominal voltage of 3.2V. When selecting, it is necessary to ensure that the voltage of the battery matches the requirements of the equipment, otherwise it may cause the equipment to malfunction or be damaged.
⑥ Security performance
Safety performance is one of the most important factors in the selection of 18650 batteries. High quality 18650 batteries should have good safety protection devices that can prevent abnormal situations such as short circuits, overcharging, overdischarging, and high temperatures from occurring. In addition, attention should also be paid to the safety certification of batteries, such as CE, UL, PSE, etc. These certification marks indicate that the battery has passed international or national safety standard testing, making it more reassuring to use.
⑦ Temperature adaptability
Temperature has a significant impact on the performance and lifespan of 18650 batteries. Generally speaking, the operating temperature range of 18650 batteries is -20 ℃ to 60 ℃, but at extreme temperatures, the performance of the battery will decrease. For example, in low-temperature environments, the discharge capacity of batteries will decrease; In high temperature environments, the lifespan of batteries will be shortened. Therefore, when selecting, the appropriate battery should be chosen according to the usage environment of the equipment.
⑧ Cycle life
Cycle life refers to the number of charge and discharge cycles that a battery can perform while maintaining a certain capacity. High cycle life means that the battery has a longer lifespan and can reduce the cost of long-term use. Generally speaking, the cycle life of high-quality 18650 batteries can reach hundreds to thousands of times. When selecting, it is advisable to choose batteries with longer cycle life as the overall product lifespan will be longer.
⑨ Battery shape
18650 batteries are divided into two types: flat head and pointed head. Flat head batteries do not have protective covers, while pointed batteries have protective covers to prevent overcharging. When selecting, the appropriate battery shape should be chosen according to the requirements of the equipment.
⑩ Other factors
In addition to the above factors, the weight, size, production date, etc. of the battery should also be considered. For example, the weight and size of the battery can affect the overall design and portability of the device. In addition, batteries with a production date as close as possible should be selected to ensure their performance and lifespan.
Application scenarios and selection suggestions
① Consumer Electronics
In the field of consumer electronics, such as laptops, digital cameras, etc., it is usually necessary to consider the energy density and cycle life of batteries. For example, laptops require 18650 batteries with large capacity and long cycle life to meet the needs of long-term use. It is recommended to choose a battery with a capacity between 2500mAh and 3000mAh and a cycle life of over 500 times.
② Electric tools
Electric tools have high requirements for the discharge capacity of batteries. For example, devices such as electric wrenches and electric scissors require high discharge current batteries to ensure efficient operation of the tools. Therefore, 18650 batteries with high discharge capacity (such as 3C or above) should be selected.
③ Electric vehicles
Electric vehicles have extremely high requirements for battery energy density, cycle life, and safety. For example, early models of Tesla Model S and X used a large number of 18650 batteries to form battery packs. When selecting, batteries with high energy density, long cycle life, and excellent safety performance should be chosen.
④ Portable devices
In portable devices such as power banks and high-intensity flashlights, battery capacity and portability need to be considered. For example, a power bank requires a high-capacity 18650 battery to meet the long-term usage needs of users. It is recommended to choose a battery with a capacity between 2500mAh and 3000mAh.
18650 batteries play an important role in the market due to their excellent performance and wide range of applications. However, when selecting, multiple factors such as brand, capacity, continuous discharge current, internal resistance, voltage, safety performance, temperature adaptability, and cycle life need to be comprehensively considered. Only by selecting the appropriate 18650 battery can the safety, efficient operation, and long-term use of the equipment be ensured.
